Projectile weapon aiming systems are discussed herein principally with reference to their use on rifles and embodied in telescopic sights commonly known as riflescopes. It will become apparent, however, that projectile weapon aiming systems may include aiming devices other than riflescopes, such as reflex sights and bow sights for example, and may be used on weapons other than rifles, which are capable of propelling projectiles along substantially predeterminable initial trajectories, e.g., handguns, shotguns, bows, crossbows, artillery, and the like.
A factor that must be taken into account in long-range shooting is the curved trajectory traversed by a bullet or other projectile as it falls from its initial trajectory while traveling the distance from the projectile weapon to the target, i.e., “range.” An aiming line of sight extending through a reticle aiming mark of, for example, a riflescope rigidly affixed to the gun, is straight and hence the line of sight can intersect the curved trajectory only at a discrete range. The range at which the line of sight (as determined by the reticle) intersects the curved trajectory of the projectile may also be referred to as the sighted-in distance or sighted-in range. At other ranges the projectile will travel below or above the aiming line of sight, necessitating the use of elevation adjustments to sight-in the projectile weapon at the new range. For either case (e.g., sighting-in a projectile weapon to a predetermined range, for example 100 yards, or adjusting the weapon to be sighted-in at another range) elevation adjustments in such riflescopes are typically made by turning an adjustment mechanism of the riflescope to impart vertical movement of optical elements to adjust the line of sight (as described, for example, in U.S. Pat. No. 3,297,389 to Gibson) or of the reticle to adjust the line of sight (as described, for example, in U.S. Pat. No. 3,058,391 to Leupold), so that the weapon and riflescope are accurately sighted-in to another range (e.g., the range of a target). To adjust for the effect of crosswinds, riflescopes also typically include a separate windage adjustment mechanism for imparting horizontal movement to the optical elements or reticle. In yet other projectile weapon aiming systems, the entire aiming device is adjusted relative to the weapon via an adjustable sight mount.
Adjustment of the elevation and windage is time consuming and may require the shooter to take his or her eyes off the target while manipulating the adjustment mechanisms or measurement tools. For example, U.S. Pat. No. 6,196,455 to Robinson discloses a hand-held analog calculator that, in conjunction with a mil-dot reticle, permits a shooter to determine the range to the target and the necessary elevation adjustment (e.g., in mil-dots or portions thereof) to compensate for bullet drop. U.S. Pat. No. 6,516,699 to Sammut et al. discloses a similar function performed by a hand-held personal digital assistant (“PDA”) that enables the user to input information regarding weather, gun and ammunition characteristics, and target information, including range to target. The PDA calculates the adjustments that need to be made to a conventional scope, or the location on the reticle that should be used as an aiming point, in order to hit the target. Both the Robinson device and Sammut device require that the shooter withdraw their attention from their scope.
Consequently, many hunters and military marksmen use ballistic compensation reticles that provide multiple aiming points for aiming at different distances or under different wind conditions. Such reticles employ a ballistic adjustment technique known as holdover (or “come-up”) and holdunder (or “come-down”) in which the user merely aims the weapon high or low to adjust for ranges different from the sighted-in range. One such ballistic reticle is sold by Leupold & Stevens, Inc. of Beaverton, Oreg., USA under the trademarks BALLISTIC AIMING SYSTEM® and BAS®. Ballistic compensation reticles of this type are also described in U.S. patent application Ser. No. 10/933,856, filed Sep. 3, 2004 and published as US 2005/0229468 A1 and is incorporated herein by reference.
Similarly, U.S. Pat. Nos. 6,591,537 and 7,069,684 to Smith both describe a gun sight reticle defining a system of dimensioned indicia spaced at specific separations to improve aiming accuracy of, for example, a rifle. For each, in addition to the horizontal hairline, the reticle includes four horizontal range-marker lines disposed at specific angular separations below the horizontal hairline in bisected relationship with the center vertical hairline. The spacing of the range marker lines below the center horizontal hairline is proportional to bullet drop at selected ranges. Further, the relative lengths of the range-marking bars on each side of the central vertical crosshair are proportional to a 10 mile per hour crosswind at the target range reflected by each respective range marker.
Rangefinding and/or ballistic compensation reticles have several deficiencies. First, they tend to clutter the field of view, which can inhibit target acquisition and visibility. Second, the number of different discrete ranges for which there are secondary aiming marks is limited and for ranges falling in between those corresponding to the secondary aiming marks, the user must interpolate or guesstimate as to the proper holdover. A similar issue applies to windage adjustments.
Handheld laser rangefinders are now available that allow a user to quickly determine a range to target. Some such rangefinders also include an inclinometer for determining the inclination to target. Inexpensive remote sensors are also available for determining environmental conditions affecting ballistics, including anemometers for detecting wind conditions. For example, U.S. patent application Ser. No. 11/555,591, filed Nov. 1, 2006 and titled “BALLISTIC RANGING METHODS AND SYSTEMS FOR INCLINED SHOOTING” (“the '591 application”), which is incorporated herein by reference, describes a handheld rangefinder including an inclinometer, sensors, a computer processor, and ballistics software for accurately determining aiming adjustment recommendations for a hunter or marksman.
The present inventor has recognized the desirability of simplifying the process of making aiming adjustments to account for ballistics at different ranges and inclinations, for different bullets or projectile types, and other ballistic factors, while achieving a desired degree of accuracy in aim so as to promote taking responsible shots at distant targets.